The world of polymers has progressed rapidly to transform material science from wood and metals of the 19th Century to the use of thermoset polymers of the mid-20th Century to the use of thermoplastic polymers of later 20th Century.
Thermoplastic elastomers (TPEs) combine the benefits of elastomeric properties of thermoset polymers, such as vulcanized rubber, with the processing properties of thermoplastic polymers. Therefore, TPEs are preferred because they can be made into articles using injection molding equipment.
Thermal capacity, also known as heat capacity, can be expressed with respect to an object as the ratio between the amount of heat energy transferred to the object and the resulting increase in temperature of the object.
Every substance has a thermal capacity. Metals generally have very little thermal capacity and dissipate heat almost as quickly as the metallic object is heated. Water generally has a large thermal capacity and retains heat for a considerable period of time, dissipating heat only very slowly.
These thermodynamic principles have practical effects and advantages in materials science. Polymeric materials with a good thermal capacity can serve as heat absorbers or heat dissipators depending on the relative temperatures at the interfaces between those polymeric materials and their contiguous materials. A heating pad can soothe tired and sore back muscles after considerable exertion. An ice pack can reduce swelling at a twisted ankle. Either way in these examples, the capacity to obtain and retain heat or cold allows materials to give therapeutic relief.